The MAX4978–MAX4981 overvoltage-protection devices protect low-voltage systems against voltage faults up to +28V and feature a low 85mΩ R_ON FET, an active current limiter, and lithium-ion battery overcharge protection (MAX4980/MAX4981). These devices are used to protect the charger input port on a portable device.

The overvoltage protector feature protects against voltages up to 28V with two different trip thresholds: 5.7V (MAX4978/MAX4980/MAX4981) and 6.8V (MAX4979). There is an undervoltage protector with two different trip thresholds: 4.4V (MAX4978) and 2.63V (MAX4979/MAX4980/MAX4981).

The overcurrent limiter and battery voltage monitor features provide a second layer of protection for a lithiumion battery charger. The overcurrent limiter is available in two different thresholds: 0.9A (MAX4978/MAX4979/MAX4980) and 1.95A (MAX4981). Once current reaches the threshold, it is held for a 20ms blanking time. If the current is still at the limit after the blanking time, the FET is turned off, and the device restarts the cycle after 160ms. The battery voltage monitor measures the voltage of a lithium-ion battery and disables the FET if the battery voltage reaches 4.4V (MAX4980/MAX4981).

The MAX4978–MAX4981 are available in a small 8-pin TDFN (2mm x 3mm) package and are specified over the extended -40°C to +85°C temperature range.